IUCAA Preprints
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Item Search for continuous gravitational wave signals from sources in binary system(2015-03-01) Dhurandhar, S.V.; Vecchio, AlbertWe analyze the computational costs of searches for continuous monochromatic gravitational waves emitted by rotating neutron stars orbiting a companion object. As a function of the relevant orbital parameters, we address the computational load involved in targeted searches, where the position of the source is known; the results are applied to known binary radio pulsars and Sco-Xl.Item Squeezing and dual recycling in laser interferometric gravitational wave detectors(2015-02-18) Bhawal, Biplab; Chickarmane, VijayWe calculate the response of an ideal Michelson interferometer incorporating both dual recycling and squeezed light to gravitational waves. The photon counting noise has contributions from the light which is sent in through the input ports as well as the vacuum Modes at sideband frequencies generated by the gravitational waves. The minimum. detectable gravity wave amplitude depends on the frequency of the wave as well as squeezing and recycling parameters. Both squeezing and the broadband operation of dual recycling reduce the photon counting noise and hence the two techniques can be used together to make more accurate phase measurements. The variance of photon number is found to be time-dependent. Oscillating at the gravity wave frequency but of much lower order than the constant part.Item Coincidence detection of broadband signals by networks of the planned interferometric gravitational wave detectors(2015-01-25) Bhawal, Biplab; Dhurandhar, S.V.We describe how the six planned detectors (2 LIGOs, VIRGO, GEO, AIGO, TAMA) can be used to perform coincidence experiments for the detection of broadband signals from either coalescing compact binaries or burst sources. We make comparisons of the achievable sensitivities of these detectors under different optical configurations and find that a meaningful coincidence experiment for the detection of coalescing binary signals can only be performed by a network where the LIGOs and VIRGO are operated in power recycling mode and other medium scale detectors are operated in dual recycling mode. For the model of burst waveform considered by us (i.e. uniform power upto 2000Hz), we find that the relative sensitivity of the power-recycled VIRGO is quite high as compared to others with their present design parameters and thus coincidence experiment performed by including VIRGO in the network would not be a meaningful one. We also calculate optimized values for the time-delay window sizes for different possible networks. The effect of filtering on the calculation of thresholds has also been discussed. We set the thresholds for different detectors and find out the volume of sky that can be covered by different possible networks and the corresponding rate of detection of coalescing binaries in the beginning of the next century. We note that a coincidence experiment of power-recycled LIGOs and VIRGO and dual-recycled GEO and AIGO can increase the volume of the sky covered by 3.2 times as compared with only the power-recycled LIGO detectors and by 1.7 times the sky covered by the power-recycled LIGO-VIRGO network. These values are far less than the range that can be covered by only the LIGO-VIRGO network with dual recycling operation at a later stage, but the accuracy in the determination of direction, distance and other source parameters will be much better in a coincidence experiment in which other detectors and especially AIGO take part.Item Matching of the continuous gravitational wave in an all sky search(2011-07-05) Sahay, S. K.We investigate the matching of continuous gravitational wave (CGW) signals in an all sky search with reference to Earth based laser interferometric detectors. We consider the source location as the parameters of the signal manifold and templates corresponding to different source locations. It has been found that the matching of signals from locations in the sky that differ in their co-latitude and longitude by π radians decreases with source frequency. We have also made an analysis with the other parameters affecting the symmetries. We observe that it may not be relevant to ake care of the symmetries in the sky locations for the search of CGWfrom the output of LIGO-I, GEO600 and TAMA detectors.Item GInflationary hubble parameter from the gravitational wave spectrum in the general slow-roll approximation(2006-06-06)We derive first and second order general slow-roll inverse formulae giving the Hubble parameter H in terms of the gravitational wave spectrum. We also derive improved forward general slow-roll formulae giving the gravitational wave spectrum in terms of the Hubble parameter H. Moreover, the general slow-roll consistency condition relating the scalar and tensor spectra is obtained.Item AIGO: a southern hemisphere detector for the worldwide array of ground based interferometric gravitational wave detectors(2009-10-01) Dhurandhar, Sanjeev; Souradeep, Tarun; Coward, DThis paper describes the proposed AlGO detector for the worldwide array of interferometric gravitational wave detectors. The first part of the paper summarises the benefits that AlGO provides to the worldwide array of detectors. The second part gives a technical description of the detector, which will follow closely the Advanced LIGO design. Possible technical variations in the design are discussed.Item Coherent versus coincidence detection of gravitational wave signals from compact inspiraling binaries(2010-03-30) Dhurandhar, Sanjeev; Mukhopadhyay, Himan; Tagoshi, H.; et al.We compare two multi-detector detection strategies, namely, the coincidence and the coherent, for the detection of spinless inspiraling compact binary gravitational wave (GW) signals. The coincident strategy treats the detectors as if they are isolated - com- pares individual detector statistics with their respective thresholds while the coherent strategy combines the detector network data phase coherently to obtain a single detection statistic which is then compared with a single threshold. In the case of geographically separated detectors, we also consider an enhanced coincidence strategy because the usual (naive) coincidence strategy yields poor results for misaligned detectors. For simplicity, we consider detector pairs having the same power spectral density of noise, as that of initial LIGO and also assume the noise to be stationary and Gaussian. We compare the performances of the methods by plotting the receiver operating characteristic (ROC) for the two strategies. A single astrophysical source as well as a distribution of sources is considered. We find that the coherent strategy performs better than the two coincident strategies under the assumptions of stationary Gaussian detector noise.